1. Field of the Invention
The present invention relates to a control device for controlling a servomotor of a machine tool or industrial machine using a CNC (numerical control device), and more specifically, to a control device that improves the system of setting and adjusting various parameters that are necessary for servo system control.
2. Description of the Related Art
When using a CNC (numerical control device) to control machine tools, industrial machines and the like that are driven by a servomotor, it is necessary to set various parameters and when necessary to adjust what has been set. Generally, there are the following two types of parameters that require this sort of setting and adjusting.
(1) Parameters that regulate the content of servo system control:
(2) Parameters for deciding how commands are issued:
Examples of (1) include parameters that determine the gain of the position loop, speed loop, and current loop, and the filter constant to avoid mechanical resonance. Examples of (2) are parameters for deciding how commands such as acceleration and deceleration time constants and the method of corner deceleration are issued. More specifically, this includes the way to apply acceleration and deceleration time constants before and after interpolation, the corner deceleration, the deceleration due to the command acceleration, and the deceleration due to the change in acceleration.
Of the parameters that are broadly divided into (1) and (2) above, the parameters in (1) for performing servo system control have a general feature that enables to almost uniquely determine the optimal value for achieving best performance, once the mechanical system has been determined. However, in respect of the parameters in (2) for deciding how commands are issued, when looked at from this perspective, a state of affairs exists that makes it difficult to decide on the optimal values. For example in the case of mechanical tools, the parameter values that ought to be selected differ according to whether reducing the machining time is given priority, or whether increasing the machining accuracy is given priority. Moreover, since there are a number of parameters that influence machining time and machining accuracy, the problem arises as to how to combine the parameters to obtain the desired results.
Conventionally, in the case of parameters of type (2) such as the way to apply acceleration and deceleration time constants before and after interpolation, the corner deceleration, the deceleration due to a command acceleration, and the deceleration due to the change in acceleration, these parameters are not independently adjusted in response to the characteristics that are required for the machine or for machining. Instead a technique whereby parameter values are modified in a certain regular way has become widely known. However, in order to fulfill required specifications (requirements for example as to length of machining time and the degree of machining accuracy) to the greatest possible extent, it is necessary to modify a number of parameters simultaneously. For general users, this kind of adjustment is not easy, and it is necessary to have a high degree of skill in order to perform systematic adjustments to obtain results in accordance with the requirements.
In order to cope with this problem, a technique to simplify the setting and switching of parameters has been proposed, and is currently in use, whereby xe2x80x9cparameter sets consisting of several kinds of parametersxe2x80x9d, each constituted in response to needs such as priority to accuracy, priority to speed, and priority to shock reduction, based on a number of sample settings, are prepared inside the CNC, so that a user switches parameters by choosing from these parameter sets the set the user considers optimal.
If this technique is used, it is only necessary to choose one parameter set from an index that gives priority to either accuracy, speed or shock, thereby making it easier for a general user to set the parameters according to their objective. However, even using this technique, since parameter sets are prepared using discrete values, it is impossible to take into account an operator""s wish to give xe2x80x9ca bit more priority to accuracyxe2x80x9d, xe2x80x9ca bit more priority to speedxe2x80x9d or xe2x80x9ca bit more priority to shock reductionxe2x80x9d.
The object of the present invention is to improve the conventional control device of the type that prepares the above-mentioned parameter set, and enable the easy achievement of parameter adjustment so as to obtain results that are closer to the conditions desired by an operator.
In order to achieve this object, the present invention is able to create a new parameter set (intermediate parameter set) which includes an intermediate value of the discrete parameters, by an interpolation calculation using an interpolation coefficient, from the discretely prepared parameter sets.
The present invention consists of a servo control section that drives the servomotor and a numerical control section that provides operating commands to the servo control section. The present invention is applied to a control device for driving and controlling a servomotor based on several types of control parameters that regulate the operation of the servo control section and several types of control parameters that regulate the operation of the numerical control section.
The control device according to the present invention comprises a means for forming one or more groups with regard to one or more types of control parameters and storing a plurality of parameter sets each composed of individual parameter values in the groups; a means for selecting at least two sets from among the plurality of parameter sets; and a means for setting an index for providing any intermediate value with regard to corresponding parameter values in the two or more parameter sets selected. The present invention has the characteristic of driving and controlling a servomotor based on the intermediate value of each parameter in the parameter set, according to the index provided.
In this case, the storage means and the means for setting the index may be built into a computer that is connected to the control device. In a typical embodiment, the control parameter set for the numerical control section consists of a combination of at least one of acceleration and deceleration time constants, corner deceleration, permissible acceleration value, and permissible acceleration change amount. Further, the index for setting the intermediate value may be, for example, an index based on the machining time or the operation time of the machine, the machining accuracy of the machine, or the size of the shock accompanying acceleration and deceleration of the machine.
In addition, the formula for calculating the intermediate value of the two parameter sets can be expressed as intermediate value=(1xe2x88x92S)xc3x97xcex1+Sxc3x97xcex2 for example, where the parameter value of one parameter set is xcex1, the parameter value of the other parameter set is xcex2, and the index is set to S (0xe2x89xa6Sxe2x89xa61).